He was certainly a superhero of a kind, just one whose powers mainly consisted of consuming copious amounts of alcohol while still, somehow, churning out wildly colorful, raging dispatches from the road.

"The Rum Diary" is based on Thompson's heavily autobiographical novel by the same name, which he wrote as a 22-year-old in the early 1960s after a stint as a newspaper reporter in San Juan, Puerto Rico. It wasn't published until 1998. Since then, Thompson's friend Johnny Depp (who also played Thompson in 1998's "Fear and Loathing in Las Vegas") has been trying to adapt "The Rum Diary" to the screen.

"The Rum Diary" — which is dedicated to Thompson, who died in 2005 — is essentially a portrait of the Duke as a young journalist. The stand-in for Thompson, the young novelist-reporter Paul Kemp (Depp), is trying to find his way and his writing voice: It's the birth of Gonzo.

Criminally exaggerated resume in hand, Kemp has gone to Puerto Rico to try his hand as a reporter. He lands a job at the San Juan Star, whose editor-in-chief, Lotterman (the excellent Richard Jenkins), is at his wit's end running a failing, diminishing daily. As he interviews a hung-over Kemp, he quizzes him on what kind of drinker he is, to which Kemp deadpans that he's at "the upper-end of social."

Kemp is befriended by staff photographer Sala (Michael Rispoli, in a deservedly big part for him), a burly, genial newsman who is nevertheless not once seen with a camera in hand.

Kemp moves into Sala's dilapidated dump of an apartment, which he shares with crime reporter Moberg (Giovanni Ribisi), a horse-voiced, over-drugged oddity who listens to Hitler broadcasts and sets some kind of record for caustic reporter-editor relations.

Kemp catches the attention of American businessman Sanderson (Aaron Eckhart), a smooth manipulator who is trying to push through an enormous development of a nearby, pristine island that's pushing locals out in favor of American investors. Sanderson recruits Kemp to spin the development favorably in the Star.

This picture of American corruption of Puerto Rico is one of the more compelling aspects of "The Rum Diary." A combative atmosphere between poor locals and rich Americans hangs in the air, as do the Navy bombing tests on Vieques. Depp is again in the Caribbean among pirates.

Sanderson's slick, wealthy appeal is tempting to Kemp, who isn't finding the constricting Star to be an especially noble pursuit, either.

Even more alluring is Sanderson's beautiful fiancee Chenault, played by Amber Heard. Kemp immediately falls for her ("Oh God, why did she have to happen?" he mutters after meeting her) and it's no wonder: Heard is a stunning presence.

This builds slowly for Kemp into a moral crisis and, finally, an artistic tipping-point. "I don't know how to write like me," he says, but by the end of the film, it's clear that Kemp/Thompson has found his legs. The guiding principle is a furious distrust of authority (we glimpse him cursing Nixon), and a key ingredient is hallucinogens (we also get an early encounter with LSD).

You might expect a tribute such as this to be sycophantic, but director Bruce Robinson (famous for the brilliant cult film "Withnail & I") keeps a realistic tone. Robinson, who also wrote the screenplay adaptation, doesn't present the cartoonish Thompson we've come to expect. It's a refreshing, grounded view of the writer.

Depp, at this point, would seem to not be aging. This more low-key performance as a Thompson alter-ego feels truer than the manic derangement of "Fear and Loathing," but the role is also lacking yearning and real energy.

Thompson went on to find his voice, but "The Rum Diary," entertaining and well-intended, comes just shy of discovering its own.

"The Rum Diary," a FilmDistrict release, is rated R for language, brief drug use and sexuality. Running time: 120 minutes.

2½ stars out of four.

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